The invention relates to superconductive bearings and in particular to a method and apparatus of operating a structure of a rotor in an equilibrium stable state within a stator by use of superconductive bearings.
Bearings have found a widespread use through-out time to enable movement of one mechanical part with respect to another. In one application, a bearing structure may enable movement of a wheel with respect to a axis in which a rotary part such as a wagon wheel rotates around a stationary part such as the wagon axle. In another application, rotating apparatus such as a rotor is positioned within stationary apparatus such as a stator like as in various types of electric motors so that the rotor rotates within the stator. In prior art bearing structures, the constant and long term rotation of a rotating part with respect to a stationary part causes an undue amount of wear on parts of the rotor and stator that are in movable contact with each other and thereby may result in an uneven movement of one part with another and even failure of the bearing structures.
Various techniques have been used to lessen and even prevent the wear of the moving parts. Even in very early times the wear problem was recognized and various types of lubricants have been applied as a thin film between the rotating parts to reduce friction, heat and wear. In addition, it was recognized that various types of materials could be developed and used with new lubricants to reduce the wear of the bearing parts and to improve operation of the bearing structures.
Attempts have also been made to suspend a moving part independently of a stationary part so as to prevent one part from engaging another and thereby reduce friction, wear and heat. Permanent magnets have been used in past bearing structures to generate opposing magnetic flux fields between a housing and an inner rotating member to repulse one moving part from another. In one such bearing structure, various configured iron rings were alternately mounted with axially magnetized rings on both a rotor and stator in which like poles on and between the rotor and stator face one and another to provide repulsion between the rotor and stator. A problem arises in this arrangement due to the unevenness in the fields generated by minor differences occurring in the ring configurations. One solution to prevent the minor differences from occurring was to install alternate iron rings and radially polarized magnets on both the rotor and stator. In another application, magnets were provided on a bearing rotor and a pair of coils were installed on a stator and pulsed to avoid a vibrational resonance condition between the stator and rotor. Another application, was to make a rotor operate independently of the stator by having one set of rings generating an axially aligned field and another set of rings generating a radially aligned field such that one member was suspended within another without contact. Again, problems exist in these designs due to the inconsistencies in the magnetized members.
Various bearing apparatus in the prior art have been designed to use superconducting material to improve operation of a rotor within fixed stators. In one design, a superconducting rotor is constructed with a magnetic pole at each end of the rotor with the poles resting in a bearing. A bath cools the apparatus such that the rotor is elevated with respect to the fixed bearing. Superconducting coils have been used with both rotor and stator apparatus to develop a repulsive force between the fixed stator and a movable rotor. Methods have been developed for charging superconductive coils constructed of niobiumtitanium and niobium-tin materials submerged in a cooling agent. Thermocouples, one located outside the cooling agent and another located in the cooling agent, are wired in series with the coil and serve to provide a current. One particular bearing structure has circular superconductive coils mounted within a disk of the rotor and has fixed superconductive coils mounted within the stator in a plane parallel to a plane of the rotor coils. The stator coils are positioned directly opposite the rotor coils and generate a repulsive force. Apparatus has also been developed to achieve a current circulating circuit in the winding of a superconducting magnet.
Although superconductive bearing apparatus has been developed in the prior art, a problem arises of instability of operation and super conductive bearing apparatus is needed to reduce magnetic field inhomogeneities which produce vibration between the stator and rotor in superconductive bearings.
It is an object of the invention for a superconductive magnetic bearing structure to support a rotor with respect to the stator in a free stable state.
It is another object of the invention for a superconductive bearing to have a rotor with closed rotor loops each formed of a superconductive material having zero electrical resistance at a temperature below a superconductivity transition temperature.
It is another object of the invention for a superconductive bearing to have closed stator loops formed of the superconductive material and angularly mounted on a stator around the closed rotor loops.
It is another object of the invention for a superconductive bearing to have a rotor with closed rotor loops each formed of a superconductive material having zero electrical resistance at a temperature below a superconductivity transition temperature and a stator enclosing the rotor and having closed stator loops formed of the superconductive material and angularly positioned around one of the closed rotor loops and cooled below the superconductivity transition temperature to establish frozen magnetic linkages between the closed rotor and stator closed loops to form the superconductive bearing supporting a rotation of the rotor in an equilibrium stable state within the stator.
It is another object of the invention for a superconductive bearing to have two-state switches each having resistive and shorting states for use with closed rotor and stator loops for enabling energization of the closed rotor and stator loops to establish frozen magnetic linkages therebetween.
In a preferred embodiment of the invention, apparatus for supporting a rotor with superconducting bearings in a stator has a rotor with a pair of closed rotor loops each formed of a planar short-circuited coil wound of a superconductive wire having zero electrical resistance at a temperature below a superconductivity transition temperature and which are mounted on a shaft of the rotor at each end of the rotor. A stator encloses the rotor and has closed stator loops formed as planar short-circuited coils wound of the superconductive wire and are configured to have two non-equal circular-arc sides joined at the ends thereof by radial segments and each is angularly positioned at ends of the stator around one of the closed rotor loops. A two-state switch having a resistive and a short state is formed of coils of wire wound around a section of the planar short-circuited coils of the closed stator loops. A cooling agent cools the closed rotor and stator closed loops to a temperature below the superconductivity transition temperature. Apparatus energizes the cooled closed rotor and stator loops and the two-state switch and establishes frozen magnetic linkages between the closed rotor and stator closed loops and forms a superconductive bearing supporting a rotation of the rotor in an equilibrium stable state within the stator. Sensors mounted on the stator within a magnetic field zone of the closed stator and rotor loops frozen magnetic linkages registers linear shifts and angular declinations of the rotor relative to the stator.
In another embodiment of the invention, a planar superconductive bearing structure has a rotatable member formed as a short-circuited coil wound of a superconductive wire having zero electrical resistance at a temperature below a superconductivity transition temperature. A plurality of stationary member closed loops are formed as a planar short-circuited coils wound of the superconductive wire configured to have two non-equal circular-arc sides joined at the ends thereof by radial segments are each angularly positioned around the closed rotatable member. A cooling agent cools the closed rotatable and stationary member closed loops to a temperature below the superconductivity transition temperature. Apparatus energizes the cooled rotatable and stationary member closed loops and establishes frozen magnetic linkages therebetween forming a superconductive bearing supporting a rotation of the rotatable member in an equilibrium stable state within the stationary members.
In another embodiment of the invention, a method of supporting a rotor within a stator by superconducting magnetic bearings comprises a step of arresting the rotor having closed rotor loops with respect to the stator having closed stator loops adjacent the closed rotor loops wherein the closed loops are formed of a superconductive material. The method cools the rotor and stator closed loops to a temperature below a superconductivity transition temperature and establishes a zero electric resistance of the closed loops. The method enables a small portion of the cooled rotor and the stator closed loops to assume a resistance state and applies a current through the resistance state of the cooled rotor and stator closed loops to generate frozen magnetic linkages between the rotor and stator closed loops. The rotor is then freed to rotate in an equilibrium stable state within the stator.